abscission africa anthocyanin antler asia aspen australia auxin birch botany carotenoid deciduous teeth deer digital object identifier dry season elm europe evergreen flower forsythia genus honeysuckle horticulture insect larch latin leaf madagascar maple metasequoia north america oak parenchyma plant plant hormone poison ivy polar climate pollination rain semi-deciduous south america temperate deciduous forest tree tropical and subtropical dry broadleaf forests viburnum virginia creeper vitis wisteria